So-called hydropneumatic struts are known from the prior art which have a cylinder and a piston longitudinally displaceably received in the cylinder and whose piston chamber is in communication with a hydraulic accumulator. The hydraulic accumulator is generally a hydraulic accumulator containing hydraulic fluid and moreover containing a compressible gas volume. On a movement of the rail vehicle, hydraulic fluid is guided out of the piston chamber into the hydraulic accumulator or out of the hydraulic accumulator into the piston chamber, with the said compressible gas volume having resilient properties so that the hydropneumatic strut acts as a spring element. In this connection, each hydropneumatic strut is typically connected to its own hydraulic accumulator, whereby a comparatively complex design results.
It is the object of the present disclosure to provide a spring system of the first named type which has a simpler structure.
This object may be solved by a spring system having a strut for arrangement between a dolly and a body of a rail vehicle, the strut having a cylinder and a piston displaceably received in the cylinder which bound a piston chamber, with the piston or the cylinder being connectable to the dolly and the other of the components being connectable to the body and with one or more springs which cushion the body with respect to the dolly. Further, a non-resilient hydraulic system is provided which is in communication with the piston chamber and by means of which the amount of the hydraulic medium in the piston chamber can be varied for the purpose of adjusting the strut length. Furthermore, an abutment member is provided by means of which the end position of the piston in the cylinder can be changed, with means being provided which are designed such that they actuate the abutment member when the piston chamber or the hydraulic system is pressure-less or when the pressure in the piston chamber or in the hydraulic system falls below a value.
The hydraulic system in communication with the piston chamber does not have any resilient properties. The first named hydraulic accumulators known from the prior art may not be provided. It rather serves the adjustment of the strut length and thus the variation of the vehicle height between different operating states such as between the traveling operation and the standing of the rail vehicle at the station.
The suspension of the rail vehicle is thus not ensured by the piston-in-cylinder unit or by the hydraulic system in communication with it, but is ensured by one or more springs which cushion the body with respect to the dolly.
If it is found that the pressure in the hydraulic system or in the piston chamber drops below a limit value or if the system becomes pressure-less, the abutment member is actuated, which has the result that the end position of the piston in the cylinder is changed. In emergency operation, the actuated abutment member has the result that the piston can no longer be moved so far into the cylinder as is the case with a non-actuated abutment. A minimum vehicle height is ensured in this manner.
The abutment member can be made displaceable in the direction of movement of the piston or in a direction extending obliquely or perpendicular thereto. It is possible that the piston has a hollow space at least sectionally and that the abutment member is made displaceable relative to the hollow space of the piston. Provision can be made in this connection for the abutment member to be made such that it can be displaced between a moved-in and a pushed-out state, with it being located completely in the hollow space of the piston in the moved-in state. In this state, the abutment member thus has no influence on the piston position.
Provision is made in a further aspect of the present disclosure for the abutment member, the cylinder and the piston to be arranged concentrically to one another.
Provision is made in a further aspect of the present disclosure for the cylinder to have a section of larger diameter and a section of a diameter smaller with respect to it, with the piston being guided in both sections. It is possible that the cylinder and/or the piston has/have one or more seals which prevent a discharge of hydraulic medium from the piston chamber. The guidance of the piston in the section of the cylinder having a larger diameter can be achieved by a peripheral ring located in the end region of the piston, having bores for the passage of the hydraulic medium and furthermore serving as an abutment for the piston movement.
In a further aspect of the present disclosure, a hydraulic accumulator is provided which can be connected to a space which is arranged in the abutment member and/or is adjacent to the abutment member. The means for the actuation of the abutment member has the result that the medium flows out of the hydraulic accumulator into the said space, which in turn has the result that the abutment member is pushed out. Provision is made in a preferred aspect for this space to be adjacent to the abutment member in its end region remote from the piston chamber.
In a further aspect of the present disclosure, a check valve is provided which is arranged such that it permits a flow from the hydraulic accumulator into the space and suppresses a flow from the space into the hydraulic accumulator. It is ensured in this manner that in emergency operation, that is when the piston chamber or the hydraulic system is pressure-less or the pressure in the piston chamber or in the hydraulic system falls below a predetermined value, the abutment member remains in the actuated state in which the piston can no longer be moved fully into the cylinder, but remains in a moved-out position and thus ensures that the spacing between the body and the dolly, and thus the vehicle height, maintains a specific minimum value.
Provision is made in a further aspect for the means actuating the abutment member to comprise pressure-controlled valves. These valves are made such that they establish or cancel a connection between the said hydraulic accumulator and the space which is adjacent to the abutment member or extends in the abutment member.
Provision can furthermore be made for the means actuating the abutment member to be electrical. An embodiment is possible in which pressure sensors are arranged which sense the pressure and control valves accordingly directly or indirectly by means of a control unit such that a connection is established between the hydraulic accumulator and the space.
Provision is made in a further aspect of the present disclosure that the one or more springs are connected in series to the cylinder with the piston that is to the unit of cylinder and piston.
The springs can be one or more coil springs. It is possible that a plurality of springs are provided which are arranged concentrically to one another and/or to the piston-in-cylinder unit.
In a preferred aspect of the present disclosure, the springs extend between the cylinder and the body or between the cylinder and the dolly.
Provision is made in a further aspect of the present disclosure for the springs to be one or more coil springs extending between spring plates and for at least one further spring to be located in series with one of the spring plates and/or in the region between the cylinder and one of the spring plates. The spring located in series with one of the said spring plates can, for example, be a multilayer spring, for example a rubber spring. The spring extending between the cylinder and one of the spring plates can, for example, be a spring having a hollow space which is elastically deformed as required.